Possible role of the adhesin ace and collagen adherence in conveying resistance to disinfectants on Enterococcus faecalis.
BACKGROUND
This study aimed to evaluate whether the presence of the ace gene and Ace-mediated binding to collagen confers on Enterococcus faecalis resistance against common endodontic disinfectants.


METHODS
Isogenic strains of E. faecalis: OG1RF (wild-type) and TX5256 (ace insertion mutant of OG1RF) were grown in brain-heart infusion broth at 46 degrees C overnight. Standardized bacterial suspensions were pretreated for 1 h either with acid-soluble collagen or acidified phosphate-buffered saline (ac-PBS). Bacteria were challenged with chlorhexidine digluconate (CHX), iodine potassium-iodide (IKI), sodium hypochlorite (NaOCl), and calcium hydroxide [Ca(OH)(2)]. Samples were removed at 1, 3, and 6 h, and cultured on Todd-Hewitt agar plates. Colonies were counted, the absolute values were log transformed, and the data were statistically analyzed using Fisher's least significant differences test and t-test.


RESULTS
OG1RF was more resistant than TX5256 to IKI, NaOCl, and Ca(OH)(2) (P < 0.05). Collagen-exposed OG1RF was more resistant than the ac-PBS-pretreated OG1RF against CHX at 3 h and against IKI at 1 h (P < 0.05); no significant difference was found against NaOCl. As expected, the ace mutant strain, TX5256, pretreated with collagen or ac-PBS did not differ significantly in viability when challenged with CHX, IKI, and NaOCl. An unexpected result was found for Ca(OH)(2): collagen-pretreated OG1RF and TX5256 were both more susceptible than ac-PBS-pretreated OG1RF and TX5256, respectively (P < 0.05).


CONCLUSIONS
The presence of the ace gene confers resistance against IKI, NaOCl, and Ca(OH)(2) on E. faecalis. Exposure to collagen makes the wild-type bacterium more resistant against CHX and IKI; however, exposure to collagen apparently decreases resistance to Ca(OH)(2).
Kayaoglu
G
G
Department of Endodontics and Conservative Treatment, Faculty of Dentistry, Gazi University, Ankara, Turkey. guvenk@gazi.edu.tr
Erten
H
H
Ørstavik
D
D
D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002126:Calcium Hydroxide / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002710:Chlorhexidine / Q000031:analogs & derivatives / Q000494:pharmacology; D003094:Collagen / Q000378:metabolism*; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017613:Iodine Compounds / Q000494:pharmacology; D012388:Root Canal Irrigants / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology
C121675:Ace protein, Enterococcus; D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004202:Disinfectants; D017613:Iodine Compounds; D012388:Root Canal Irrigants; C439385:iodine potassium iodide; D003094:Collagen; D012973:Sodium Hypochlorite; C010882:chlorhexidine gluconate; D002126:Calcium Hydroxide; D002710:Chlorhexidine